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ROBERT J. TILFORD AND HENRY M. REDEMANN, OF LOUISVILLE, KENTUCKY,ASSIGNORS TO THE REDEMANN TILFORD STEEL COMPANY, OF SAME PLACE.

MANUFACTURE or STEEL.

SPECIFICATION forming part of Letters Patent No. 397,478, dated February5, 1889.

Original application filed July 25, 1888, Serial No. 281,018. Dividedand this application filed November 13, 1888 Serial No.

I 290,738. (No specimens) To all whom it may concern:

Be itknown that we, ROBERT J .TILFORD and HENRY H. REDEMANN, citizens ofthe United States,residing at Louisville, Jefferson county,

Kentucky, have invented new and useful Improvements in the Manufactureof Steel, of which the following is a specification.

Our invention relates to certain new and useful improvements in thetreatment of crude IO or low-grade steel to produce a refined orhigh-grade steel.

The most successful method of producing low-grade steel is that known asthe .Sessemer process, described in his patentof 1855;

but this product, as is well known, is suitable chiefly for railways,axles, and like uses, and is totally unsuited for structures, machinery,and tool purposes unless puddled, hammered, and rolled, for the reasonthat in its normal state it is too soft, and when hardened it becomestoo hard and brittle for the purposes stated. It was the recognition ofthese inherent defects in the Bessemer and low and medium grade steelwhich led us to the in- 2 5 vestigation of the subject which hasdeveloped our present invention, the object of which is the productionat slight cost and a minimum degree of labor of a higher grade and morerefined steel by treating the Bessemer and other low and medium gradessteel in such manner as to produce a molecular change from a coarsegrain to a line grain and silky fracture, to increase the tensilestrength, elasticity, toughness, and ductility,

3 5 and to greatly increase the carbon. \Ve have found from experiencethat uniform results in all instances flow from the treatment of metalshaving like properties.

Vith these ends in view our invention 0 consists in heating the metal tobe treated to a white heat, and then subinerging the same in a bath ofglycerine and water having added thereto spirits of niter, aqua-ammonia,chloride of ammonium, sulphate of zinc, sulphate of alumina and ammonia,substantially as will hereinafter be more particularly set forth.

In some instances we employ simply glycerinc and water for the treatmentof the metal;

but we desire to say that we lay no claim herein for such bodies alone,as they are covered by the first divisional application of our originalapplication, Serial No. 281,018, filed July 25,1888, which divisionalapplication is filed of even date herewith, this applicationconstituting the second division of our original application referredto. Neither do we lay any claim to the broad or generic idea of heatinglowgrade steel to a degree of heat represented by white heat, and thensubjecting the metal so heated to a liquid bath, (in contradistinctionto the dry or cementation process,) in which hydrocarbon or othersimilar gases are generated by contact with the heated metal and bath,as this last-named matter forms the subject of our said originalapplication.

In the practice of this our present invention we employ the severalchemical bodies in about the following proportions, to wit: 7o Spiritsof niter, one and a half (15-) ounce; aqua-ammonia, one and a half (1ounce; chloride of ammonium two (2) ounces; sulphate of zinc, one and ahalf (1.3) ounce; sulphate of alumina and annnonia, one and a half (1%)ounce; glycerine, three ounces; water, one-half (1;) gallon.

\Ve of course do not wish to confine ourselves to the exact proportionsnamed, as they may be varied within reasonable limits and yet producethe same general results; but we have found from long experience andrepeated tests and experiments that the proportions given produce thebest results. In preparing the bath we preferably first powder orgranulate the chemicals and mix the same thoroughly and intimately withthe glycerine untill well dissolved, and we then add to the bodies socompounded the necessary quantity of water. It will also be understoodthat we do not wish to confine ourselves to the exact degree of heatimparted to the metal, as that may be varied slightly, so long as theresults desired are obtained.

IVe have of course been unable to analyze the gases resulting from thecontact of the hot-metal body with the bath, but are led to believe thatthey constitute a hydrocarbon gas which has a strong alfinity for themetal, and that the latter, being in aheated state, is in such aphysical condition as to readily take up or absorb such gas; but as tothe fact that the metal is highly improved we have no doubt whatever, ashas been demonstrated by all the well-known scientific and mechanicaltests.

It will be understood, of course, that when the treatment is appliedadjacent to the furnaces where the low-grade steel is manufactured theingots may be treated without reheating, and thus the expense of suchreheating is avoided. After the metal has been subjected to thetreatment in the bath described it is allowed to cool in the ordinarymanner, and it may afterward be subjected to any ordinary hardening ortempering process, and the temper may, if necessary, be drawn and againrestored without at all affecting the other properties acquired from thebath.

lVe are of course aware that the quality of Bessemer and other low andmedium grade steel may be improved by what is known as the dry orcementation process,whieh requires a large expenditure of skilled laborand great length of time, and that, too, without always securing uniformand satisfactory results.

WVe desire it to be distinctly understood that we lay no claim to thebroad idea of illcreasing the quality of steel. by subsequent treatment,as that has been heretofore done, especially bywhatis known as thecementation process, which may be termed a dry process, our inventiondiffering from such process in the particular that it requires a periodof time amounting to a small percentage of the time required in thecementation or dry process, and is in contradistinction to such processessentially a liquid or wet process, the former requiring many days,while the latter involves only a few minutes.

As before stated, we wish it to be understood that the chief feature ofour process involves the employment of a bath having as its baseglycerine and water, for in the use of these two bodies we accomplishdesirable and improved results; but the addition to the glycerine andwater of spirits of niter, aqua-ammonia, chloride of ammonium, sulphateof zinc, and sulphate of alumina and ammonia produce better and enhancedresults; hence we Our invention or process is distinguished fromprocesses for tempering steel in oil in that by our process the nature,the physical construction, and the molecular or granular construction ofthe metal are completely changed, whereas the tempering of steel in oil,as practiced by some processes, simply tempers the metal more slowlythan is done by tempering in water and other properties, leaving themetal less hard but somewhat tougher than water-tempered material. Thechanges caused by the oil-tempering process are merely temporary, and donot change the physical or granular construction of the metal, and suchchanges as are caused thereby can be readily neutralized by reheatingand allowing the metal to cool. The changes caused by treatment by ourprocess are permanent, and cannot be removed by any known treatment orprocess without entirely destroying the steel properties of the metal byburning.

By our invention we greatly increase the tensile strength andelasticity, and yet do not destroy the per cent. of reduction ofductility, while with ordinary tempering the tensile strength andelasticity are greatly increased, but the per cent. of reduction andductility is very much impaired.

Having thus described our invention, what we. claim as new, and desireto secure by Letters Patent, is-

The process herein described for converting steel, which consists infirst heating the metal to be treated to a white heat, and then while soheated submerging the same in a liquid bath consisting of glycerine andwater in the proportion of three ounces of the former and one-halfgallon of the latter, combined with spirits of niter, one and a halfounce; aqua-ammonia, one and a half ounce; chloride of ammonium, twoounces; sulphate of zinc, one and a half ounce; sulphate of alumina andammonia, one and ahalf ounce, substantially as hereinbefore set forth.

In testimony whereof we have hereunto set our hands in the presence oftwo subscribing witnesses.

ROBERT J. TILFORD. HENRY M. REDEMANN. Witnesses:

H. J. TILFORD, DAVID BARTLEY.

